The long-term objectives of the experiments proposed in this application are the isolation and characterization of a human gene encoding a polypeptide capable of transactivating the adenovirus 5 E2 promoter. The specific approach to be taken will utilize a previously prepared cell line containing a single copy of the adenovirus 5 E2 promoter adjacent to the Tn 5 neo gene. Human genomic DNA will be transfected into these cells and cells increasing expression of the Tn 5 neo gene will be selected in G418. The specific gene responsible for this increased expression of the Tn 5 neo gene will be isolated by repeat transfection and bacteriophage cloning. Preliminary experiments have confirmed the feasibility of this approach and demonstrated the initial transfer of DNA capable of transactivating the E2 promoter. If the experiments proposed are successful, subsequent work will be directed at the further characterization of the transactivating gene and its RNA and protein products. Work from a variety of laboratories has suggested important roles for such a gene in both development and in relation to the cellular effects of a variety of viral infections. Isolation and characterization of this gene should provide additional insight into these processes.